Carbon fiber precision composite tools, molds and dies are commonly used in industry, e.g. for fabricating carbon fiber reinforced composite prototypes in the aerospace industry. Various iron-nickel alloys (Invar®, Nilo®) have a low coefficient of thermal expansion (CTE) and are used in bulk form for molds and tooling for fabricating precision composite parts. Composite parts are made e.g. by building layers of carbon cloth fibers impregnated with resin on suitable tools or molds, followed by curing in an autoclave at around 450 K (thermoset epoxy parts) or up to 725 K (thermoplastic resins). After curing the composite part is removed from the tool and the process is repeated.
Carbon fiber composite mold tooling is relatively cheap, easy to fabricate and machine; however, it is not very durable and thus is only suitable for prototypes or limited production runs. Metallic molds e.g. made of Invar® or Nilo® provide increased strength and wear resistance and higher durability but are expensive. Metallic coatings can be applied to mold/tooling substrates made from carbon composites or polymeric materials, however, the close matching of the thermal expansion coefficient of the coating layer and the substrate limits the selection of metals to InvarR and NiloR type alloys which do not possess the required mechanical strength and wear resistance to obtain the desired durability and service life, when applied as coatings versus bulk form.
In molding applications (blow, injection, compression molding and the like), for instance, it is desirable that the coefficient of thermal expansion (CTE) of the mold be it bulk metal or metal coating is closely matched to that of non-metallic (e.g. carbon fiber) composite component to avoid spring-back during heating and cooling due to CTE mismatch.
Various patents address the fabrication of molds/tooling using low CTE Invar (Ni-65% Fe alloy) to minimize material scrap generated and to reduce cost as compared to machining the die out of a metal block:
Kenney in U.S. Pat. No. 6,672,125 (2004) discloses a method for fabricating Invar based tooling by super plastically forming a tool from a planar Invar face sheet using a die with the predetermined contour. The diaphragm is heated to the super plastic temperature and pressure is applied to cause the Invar face sheet to form against the contour of the die. Super plastically forming the Invar face sheet results in a negligible amount of scrap compared to machining molds from a block and reduces the material and labor costs.
Covino in U.S. Pat. No. 5,817,267 (1998) discloses a method for fabricating a mold by providing a matrix having a shape to be molded, and spraying molten metal from a spray gun. Metals selected from the group of Fe, Ni, Zn, Al and Cu are deposited on the matrix, forming a shell, which is removed from the matrix and used as a mold. The process described reduces the cost of mold making when compared to machining large molds from solid blocks of particularly nickel alloys, containing 36-50% nickel, having a low coefficient of thermal expansion. As the thermal spray process used involves melting followed by resolidification the resulting coating is coarse grained.
Oyama in U.S. Pat. No. 5,453,173 (1995) discloses a three-dimensional electroformed shell for a mold consisting of a three-dimensional thin-walled body and an electroformed coating deposited on it. A process for manufacturing the shell is also disclosed. If the network body is made of a non-conductive material, electric conductivity is imparted to the surface e.g. by applying a conductive paint, electroless plating, vacuum evaporation or sputtering. The network body is coated with nickel using electrodeposition.
Carson in U.S. Pat. No. 3,867,264 (1975) discloses an electroforming process for replicating the surface contour of a master form. A pre-plate solution is coated on the form and comprises a combination of a metal compound capable of being reduced to its active metal constituent so as to form catalytic bonding sites for a further metal plating process, binder material comprising one or more polymer and/or polymer formers, and at least one solvent for the binder material and the metal compound. The binder material is chosen to provide a polymeric substance having poor adhesion for the form surface. The binder is dried to a polymer layer on the form and thereafter a conductive metal layer is electrolessly plated on the polymer layer. Subsequently, copper or nickel are electroplated onto the conductive layer to a desired thickness of at least 0.5 mil (12.5 μm), which is substantially greater than the thickness of the electrolessly-plated layer. In the final step the electroplated metal is removed from the form.
Various patents address the fabrication of sporting goods containing a metallic coating on a polymer substrate, particularly carbon fiber/epoxies:
Yanagioka in U.S. Pat. No. 4,188,032 (1980) discloses a nickel-plated golf club shaft made of fiber-reinforced material having on substantially its entire outer surface a metallic plating selected from the group consisting of nickel and nickel based alloys for the purpose of providing a wear-resistant coating. The electroless nickel coating of choice is 20 μm thick and the deposition time is 20 hrs, resulting in a deposition rate of 1 μm/hr.
Reed in U.S. Pat. No. 5,655,981 (1997) describes a shaft for a hockey stick comprising a non-metallic elongated material member; a first layer comprised of a resilient yet tough material bonded to the member; a second layer comprised of metal applied to the first layer by a metal deposition process; and a third layer comprised of a clear, resilient, tough material encasing said second layer of metal. The thin metallic layer is applied to the substrate by a vapor vacuum deposition process. The base layer, metallic layer and top layer have an overall thickness of less than about 3 mils. The purpose of the thin metallic layer applied to a non-metallic shaft, having a maximum thickness of 0.01 mil (0.25 μm), is entirely to enhance the appearance and the metals of choice include aluminum, copper, gold and silver.
Various patents address the fabrication of articles for a variety of applications:
Palumbo in U.S. Ser. No. 11/013,456 (2004), assigned to the same applicant, discloses articles for automotive, aerospace, manufacturing and defense industry applications including shafts or tubes used, for example, as golf club shafts, ski and hiking poles, fishing rods or bicycle frames, skate blades and snowboards that are at least partially electroplated with fine-grained layers of selected metallic materials using aqueous electrolytes. The articles are strong, ductile and lightweight and exhibit a high coefficient of restitution and a high stiffness. Suitable substrates to be coated include metallic and non-metallic materials. Suitable metal substrates include aluminum, titanium, steel, stainless steel, copper, brass, bronze, zinc, magnesium, tin and nickel, or their alloys. Non-metallic substrates include polymeric resin matrix composites employing materials including carbon fibers, ceramic matrix, aramid fibers, polyethylene fibers, boron, fiberglass, and various thermoplastics including, but not limited to, polypropylene, polyethylene, polystyrene, vinyls, acrylics, nylon and polycarbonates, among others.
Aldissi in U.S. Pat. No. 5,218,171 (1993) describes a method of fabricating wires and cables of low weight specifically for aerospace applications by silver coating an aramid fiber core to provide cables having about half the weight and about 15 times the tensile strength of cables having equivalent resistance and/or equivalently sized cores of silver plated copper. The metal coating is applied in two steps, namely by (1) electroless plating a high tensile strength fiber comprising nylon, aramid, etc., with a layer of a metal such as copper, silver; followed by (2) electroplating a second metal layer.
Burgess in U.S. Pat. No. 3,749,021 (1973) discloses a metal-plated plastic cartridge casing. A nickel or chromium metal film, preferably between 0.05 to 0.1 mils thick is plated onto a plastic cartridge case to increase the strength, abrasion and burn-through resistance as well as lubricity of the cartridge casing. The plastic casing may comprise a filled or a fiber reinforced plastic. A plated metal skin preferably 5 to 7 mils thick may also be employed in conjunction with non-reinforced plastic casings to increase the strength of the casing in selected areas.
Various patents disclose electroplating processes for the preparation of metallic coatings including Ni—Fe alloy coatings:
Tremmel in U.S. Pat. No. 3,974,044 (1976) discloses an aqueous nickel-iron alloy plating bath containing nickel ions and iron ions, a soluble non-reducing complexing agent, and a reducing saccharide selected from the group consisting of monosaccharides and disaccharides. The combination of hydroxy carboxylic acid complexers and reducing saccharide in such baths yielding high iron content bright level nickel-iron alloy deposits containing up to 50 percent iron, while retaining the Fe+3 concentration in the bath at a minimum value and reducing the amount of complexing agents required. Generally, it is preferred to utilize from about 1 to about 50 grams per liter of a reducing saccharide and from about 2 to about 100 grams per liter of the complexing agent.
Luch in U.S. Pat. No. 4,195,117 (1980) discloses the use of nickel-iron alloy strike deposits on directly plateable plastics and plated objects suitable for severe and very severe service conditions according to ANSI/ASTM specification B604-75.
Erb in U.S. Pat. No. 5,352,266 (1994), and U.S. Pat. No. 5,433,797 (1995), assigned to the same applicant, describe a process for producing nanocrystalline materials, particularly nanocrystalline nickel. The nanocrystalline material is electrodeposited onto the cathode in an aqueous acidic electrolytic cell by application of a pulsed current. The cell also optionally contains stress relievers. Products of the invention include wear resistant coatings, magnetic materials and catalysts for hydrogen evolution.
Palumbo DE 10,288,323 (2005), assigned to the same applicant, discloses a process for forming coatings or freestanding deposits of nanocrystalline metals, metal alloys or metal matrix composites. The process employs tank, drum plating or selective plating processes using aqueous electrolytes and optionally a non-stationary anode or cathode. Novel nanocrystalline metal matrix composites are disclosed as well.
Park in WO04094699A1 (2004) discloses a process for producing nano Ni—Fe alloys with a Ni content in a range of 33 to 42 wt % by electroplating, specifically a nanocrystalline Invar alloy having a grain size of 5 to 15 nm. The aqueous electrolyte comprises, on the basis of 1 liter of water, 32 to 53 g of ferrous sulfate or ferrous chloride, a mixture thereof; 97 g of nickel sulfate, nickel chloride, nickel sulfamate or a mixture thereof; 20 to 30 g of boric acid; 1 to 3 g of sodium saccharin; 0.1 to 0.3 g of sodium lauryl sulfate; and 20 to 40 g of sodium chloride. The Fe—Ni alloys exhibit excellent mechanical properties compared to the conventional polycrystalline Fe—Ni alloy and a negative coefficient of thermal expansion.
Park in WO04074550A1 (2004) discloses an aqueous electrolyte for the preparation of nanocrystalline Ni—Fe alloys having a coefficient of thermal expansion of not more than 9×10−6K−1 by electrodeposition. The aqueous electrolyte comprises, on the basis of 1 liter of water, 25 to 73 kg of ferrous sulfate or ferrous chloride or a mixture thereof, 97 g of nickel sulfate or nickel chloride or nickel sulfamate or a mixture thereof, 20 to 30 g of boric acid, 1 to 3 g of sodium saccharin, 0.1 to 0.3 g of sodium lauryl sulfate, and 20 to 40 g of sodium chloride. The Ni content of the Fe—Ni alloy produced using said electrolyte lies in the range of 20% to 50 wt %.
Bukowski in DE 10108893A1 (2002) describes the galvanic synthesis of fine-grained (group II to V or the transition elements) metals, their alloys and their semiconductors compounds using ionic liquid or molten salt electrolytes.
Various patents disclose low temperature powder spray processes for the preparation of metallic coatings:
Alkhimov in U.S. Pat. No. 5,302,414 (1991) describes a cold gas-dynamic spraying method for applying a coating to an article by introducing metal or metal alloy powders, polymer powders or mechanical mixture thereof with a particle size ranging from about 1 to about 50 microns into a gas stream. The gas and particles form a supersonic jet having a velocity of from about 300 to about 1,200 m/sec and a temperature considerably below the fusing temperature of the powder material. The jet is directed against an article of a metal, alloy or dielectric, thereby coating the article with the particles.
Tapphom in U.S. Pat. No. 6,915,964 (2005) describes a process for forming coatings by solid-state deposition and consolidation of powder particles entrained in a subsonic or sonic gas jet onto the surface of an object. Under high velocity impact and thermal plastic deformation, the powder particles adhesively bond to the substrate and cohesively bond together to form consolidated materials with metallurgical bonds. The powder particles and optionally the surface of the object are heated to a temperature that reduces yield strength and permits plastic deformation at low flow stress levels during high velocity impact, but which is not so high as to melt the powder particles.